Feature/procedure v2

[bhancockio]

https://linear.app/crewai/issue/CRE-18/pipeline

The purpose of this feature is to allow users to pipe crews together in series and parallel fashion.

To test out the pipeline feature on your own machine, I would copy some of the tests in test_pipeline.py file.

Also, the top of the pipeline.py file includes some of the key terminology you need to know to understand pipelines.

Pipeline Terminology:
Pipeline: The overall structure that defines a sequence of operations.
Stage: A distinct part of the pipeline, which can be either sequential or parallel.
Run: A specific execution of the pipeline for a given set of inputs, representing a single instance of processing through the pipeline.
Branch: Parallel executions within a stage (e.g., concurrent crew operations).
Trace: The journey of an individual input through the entire pipeline.

Example pipeline structure:
crew1 >> crew2 >> crew3

This represents a pipeline with three sequential stages:
1. crew1 is the first stage, which processes the input and passes its output to crew2.
2. crew2 is the second stage, which takes the output from crew1 as its input, processes it, and passes its output to crew3.
3. crew3 is the final stage, which takes the output from crew2 as its input and produces the final output of the pipeline.

Each input creates its own run, flowing through all stages of the pipeline.
Multiple runs can be processed concurrently, each following the defined pipeline structure.

Another example pipeline structure:
crew1 >> [crew2, crew3] >> crew4

This represents a pipeline with three stages:
1. A sequential stage (crew1)
2. A parallel stage with two branches (crew2 and crew3 executing concurrently)
3. Another sequential stage (crew4)

Each input creates its own run, flowing through all stages of the pipeline.
Multiple runs can be processed concurrently, each following the defined pipeline structure.